There are various woodworking methods employed for use in wood constructions. One method uses a specified shaped coupling to join adjacent wooden members. Specifically, in this method uses a coupling A as shown in FIG. 5 to join adjacent wooden members 100 and 110 together.
The coupling A used in this method is comprises a pair of U-shaped portions 90, 91, located on the sides of body portion 92. The body portion 92 is formed with holes 93a, 93b extending downwardly from the top thereof. The coupling A is formed as a one-piece structure made of synthetic resin having substantial structural strength.
As shown in FIG. 5, curved transition portions exist between the thinner body portion 92 and the wider U-shaped portions 90, 91. The transition portions are characterized by the radius of curvature becoming larger, little-by-little, from the bottom portion 94a to the top portion 94b. Thus, the radius of curvature of the bottom portion 94a is smaller than that of the top portion 94b.
In order to couple the wooden members with the coupling A, the joints 120, 130 of the wooden members 100, 110, respectively, must be formed in the ends thereof. The joints 120, 130 are formed to match the profile of the coupling A. Specifically, the joint 120 formed in the end of the wooden member 100, as shown in FIG. 6, has a smaller width slot a with a U-shaped lower end and a larger width slot b with a U-shaped lower end.
The same joint is formed in the end of the wooden member 110. After the ends of the wooden member 100, 110 are brought together and aligned, the coupling A is inserted into the joints 120, 130 to in the direction of the arrows shown in FIG. 5.
The coupling A, due to its configuration described above, can be insert without much resistance to approximately one-half the depth of the joints 120, 130. Then, an appropriate tool is used to further drive the coupling A fully into the joints 120, 130. This completes the method of forming a joint with the coupling A securely joining the ends of the wooden members 100, 110.
In order to form the joints 120, 130, a drill and a milling cutter are normally employed according to the following steps:
(1) on the end section of the wooden member, a small U-shaped slot a is initially drilled; PA1 (2) the milling cutter is inserted from the end section of the small U-shaped slot a of the wooden member; and PA1 (3) moving the milling cutter sideways along the smaller U-shaped slot a in a parallel manner to form the larger U-shaped slot b connecting into the smaller width slot a by a radius of curvature. PA1 (1) by the main trailing cutting edge of the groove of the body, the smaller width slot having a U-shaped bottom portion is made at the end of the wooden member; PA1 (2) simultaneously, by the bottom and side cutting edges of the end cutting blade, the larger width slot having a U-shaped slot is made at the end of the wooden member; and PA1 (3) by the curved trailing cutting edge of the groove of the body, the curved transition portions of the joint between the larger width slot and the smaller width slot are simultaneously made at the end of the wooden member.
As explained above, this conventional method requires a drill and a milling cutter. Thus, the drill and cutter need to be switched during the conventional method of making the joints. To make highly accurate joints, each time the drill and cutter are exchanged, it requires time and effort to provide an exact setting of the drill and the milling cutter on the appointed marks as well as setting the exact moving distance and direction of the tools.